Stuck in 3D printer hell. Slipping filament, thermister shorted.

For the past month I have been struggling with my mendel. This is my first reprap so I expected it to be tough, I was not prepared for this
I was printing fantastic for a month ( at 230c), even better then I expected.
Then.
One day my filament started slipping. Each day it was harder to get the filament to stay feeding.
I checked the hobbed bolt and decided I would replace it with a hyena to no avail.
I then decided that the nozzle must be jammed.
So I tried cleaning the nozzle and ended up breaking a piece of guitar string off inside the nozzle....
Yeah...

So I get a new j-head altogether because of client deadlines and still. The same thing happened.
Filament slipping after about 30 seconds of printing. Totally grinded through after 5 minutes.
After days of playing with everything from feed rates, to steps per mm on z and extruder. Nothing.


I hook it back up and I end up shorting the thermistor on itself. ( Not the first time)
I fix the wiring on the thermistor and it showed a temp at around 60c when cold. Well above ambient.
I replace the thermistor and now the temp reads 90c, these are both 100k thermistors.
Did I just kill my RAMPS?
Could the cause of all my troubles be because I shorted my ramps board and that affected something?

The heatbed reads fine and the axis are fully functioning.
How should I go about tracking down the problem.
At a total loss.

Help me Obi-wan, you're my only hope.

Edited 1 time(s). Last edit at 08/02/2012 01:27PM by emmanuelmota.

The hotend reads 90c while off and cold. I disconnect it and it reads 88c.
I connected the heatbed thermistor to the hotend thermistor connection and it also reads as 90c while off and cold.

Did I just blow out a mosfet when I shorted the thermistor? How would I test with a multi-meter?
Thanks for any help.

If you shorted the thermistor to the heater then you will have damaged the input pin of the Atmega. You can remap the firmware to a spare analogue pin and copy the thermistor circuit, which is just a 4K7 resistor to 5V and a capacitor.

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[www.hydraraptor.blogspot.com]

yeah i shorted the sensor on the j-head lol was a week of fun

basically had to replace the atmega chip as it was getting very very hot and not reading correct.

if you have to replace might be worth getting the latest atmega save you upgrading in the future if you go for LCD screen ect.

why not use some kapton tape on your thermistor wires to stop them shorting out ? (i do now)

also if you have a temp monitor check your hotend is reading close to what it should be. if its not try reflashing your firmware this solved a load of problems for me when starting out

good luck its all worth it in the long run

I replaced the arduino and I am now printing better than ever. Although I am being plauged by the "Studden Stop" issue while using a precompiled version of pronterface on a mac.
A possible fix for this is unchecking "Monitor Printer" while printing, or something to do with the python librarys on the mac itself. ! I will post back If I fix the sudden stop issue.
Thanks for the help

The sudden stop you mention, is your Arduino an R3?

Hello !
I know this is an old topic .
But can you help me figure out wich one are the spare analog input ?
I m having a hard time.
Thank you